I. Field
The following description relates generally to wireless communications, and more particularly to packet data convergence protocol (PDCP) control protocol data behavior during handover and/or connection re-establishment.
II. Background
Wireless communication systems are widely deployed to provide various types of communication; for instance, voice and/or data can be provided via such wireless communication systems. A typical wireless communication system, or network, can provide multiple users access to one or more shared resources (e.g., bandwidth, transmit power, . . . ). For instance, a system can use a variety of multiple access techniques such as Frequency Division Multiplexing (FDM), Time Division Multiplexing (TDM), Code Division Multiplexing (CDM), Orthogonal Frequency Division Multiplexing (OFDM), and others.
Generally, wireless multiple-access communication systems can simultaneously support communication for multiple mobile devices. Each mobile device can communicate with one or more base stations via transmissions on forward and reverse links. The forward link (or downlink) refers to the communication link from base stations to mobile devices, and the reverse link (or uplink) refers to the communication link from mobile devices to base stations.
Wireless communication systems oftentimes employ one or more base stations that provide a coverage area. A typical base station can transmit multiple data streams for broadcast, multicast and/or unicast services, wherein a data stream may be a stream of data that can be of independent reception interest to a mobile device. A mobile device within the coverage area of such base station can be employed to receive one, more than one, or all the data streams carried by the composite stream. Likewise, a mobile device can transmit data to the base station or another mobile device.
A layer two protocol stack (e.g., also referred to as a user-plane protocol stack) can include a packet data convergence protocol (PDCP) layer, a radio link control (RLC) layer, and a medium access control (MAC) layer. The packet data convergence protocol (PDCP) can perform services such as security, header compression, ciphering, and handoff. Security services can include ciphering to prevent others (e.g., attackers) from reading the transmitted messages and integrity protection, which prevents others from forging the identity of a user. Header compression services can compress headers of certain types of packets (e.g., IP headers, UDP headers, and RTP headers). Hand off services can include in-order delivery and selective delivery services that may include re-transmission services. The radio link control (RLC) layer can perform services, such as segmentation, concatenation, re-assembly, re-transmission, and other services that ensure that the radio link is reliable. The medium access control (MAC) layer can performs service, such as scheduling, building frames that are physically transported in the physical layer (PHY), and acknowledgement (ACK) and negative acknowledgement (NACK) services, such as hybrid ARQ (HARQ).
As a result of handover and connection re-establishment, the RLC can be reset. In order to provide lossless ordered data delivery, the PDCP utilizes a handover mode in which PDCP protocol data units (PDUs) are re-ordered and re-transmitted. A duration of time to which such re-ordering and re-transmitting occurs is dictated by a flush timer. The flush timer can ensure the delivery of data should a missing PDCP PDU is not received. Moreover, traditional techniques involve starting the flush timer when a handover command is received and a user equipment (UE) initiates re-establishment. Yet, such flush timer initiation is much earlier than when data radio bearers operation resumes which can substantially determine handover performance.